This blog was created for Niles Animal Hospital & Bird Medical Center by Peter S. Sakas DVM in an effort to provide information & discussion about animal related issues. It may move into some eccentric directions on occasion if the mood strikes me as I get more comfortable in this form of communication. I am open to suggestions & comments about the blog. Also view our hospital website www.nilesanimalhospital.com or Facebook page Niles Animal Hospital and Bird Medical Center.

Tuesday, August 26, 2014

Leptospirosis is a serious threat to our pets, leading to liver and kidney disease, yet many pet owners are totally unaware of the disease and risks. In addition, it can be prevented through the vaccination of your pet. Here is an excellent, detailed article about this disease so you can have a better understanding.

Canine leptospirosis: Growing in effect and threat

By Pedro Paulo Diniz, DVM, PhD

Assistant Professor in Small Animal Internal Medicine

Western University of Health Sciences, Pomona, CA

Despite
advances in prevention, the zoonotic disease leptospirosis is not only
widespread but growing within the US canine population. The multitude of
clinical signs and lack of an accurate in-clinic diagnostic tool make
early diagnosis of this disease a great challenge. As a consequence, 1
in 5 dogs die because of complications associated with the infection.1,2,3

The delay in suspecting the infection is the major cause of death by canine leptospirosis.

The number of seropositive dogs in the US has increased over 600% in 7 years

Leptospirosis is considered an emerging infectious disease worldwide.2
While national numbers of infected dogs are not currently available,
one large study with over 33,000 samples detected a 6-fold increase in
seropositive dogs between 2000 and 2007, following an increase in sample
testing by 5 times during the same period.4 The increase in testing reflects the veterinary community’s greater awareness regarding the risk of infection.

The more you test for canine leptospirosis, the more you may find in your area.

Not restricted to rural and wet environments anymore

Rainfall and flooding are important
factors associated with canine leptospirosis, since unvaccinated dogs
can become exposed to contaminated water and wet soil. Regions with
increased rainfall and frequent flooding, such as the Northeast,
Midwest, Gulf Coast, and Washington state, are endemic areas of canine
leptospirosis.4,5,6
However, canine leptospirosis is present throughout the contiguous
United States, even in areas of low precipitation. In fact, hot spots of
canine leptospirosis were identified in Colorado, central California,
and central Texas, among other regions.5
The leptospirosis season has 2 distinct annual peaks: during the spring
(March until May) caused by increased rainfall and standing
water/flooding, and during the fall (November and December) caused by
higher activity of wildlife reservoir hosts.4 However, canine exposure is documented year-round.

Even more startling, though historically
associated with rural environments and contact with livestock, recent
studies have demonstrated that urban areas have twice the risk for dog infection than rural areas, regardless of the dog’s age, sex, and breed.7,8
Some of the causes include the smaller proportion of vaccinated city
dogs (decreased “herd immunity”) and the active presence of reservoirs
for the pathogen.

Risk factors for canine leptospirosis
include access to marshy areas and standing water, contact with rodents
and wildlife, and living in urban areas.

The fact that the 2 most frequent Leptospira serovars in the US (L. grippotyphosa and L. pomona)9
have wildlife reservoirs (raccoons, skunks, opossums, deer) suggests
that wildlife plays a key role in the transmission of the disease in
urban and periurban environments. Raccoons have been identified as major
reservoirs of the pathogen in the US. In Colorado, 1 in 3 raccoons in
urban and suburban areas shed spirochetes in their urine.9
In addition, up to 90% of inner-city rats carry and shed Leptospira
spp.; consequently, indoor dogs with access only to backyards and local
parks are also at risk of infection.

Indoor dogs, living in both urban and
suburban areas, even with limited outdoor access, are at a similar risk
of infection to dogs in rural areas.

Am I missing leptospirosis cases?

Anorexia, fever, depression, vomiting,
and diarrhea are frequent signs of canine leptospirosis. In addition,
azotemia, elevated liver enzymes, thrombocytopenia, isosthenuria, and
proteinuria are common laboratory findings.1,2,3
However, several other diseases may cause similar signs and findings,
including hepatic, renal, and vector-borne diseases. In fact, positive
tests for vector-borne diseases serve as a marker of exposure to
wildlife and should increase clinician awareness of possible exposure to
leptospires.10

Unfortunately, the majority of cases do
not simultaneously show all typical signs, with many cases presenting
single or few atypical laboratory abnormalities such as coagulopathy,
hypoalbuminemia, or glycosuria or clinical signs such as uveitis,
cardiac manifestations, intussusceptions, or neurologic and respiratory
signs.1,2,10 Between 43% and 70% of dogs with leptospirosis have abnormal lung patterns on thoracic radiographs (interstitial lung pattern).10,11
In addition, it is believed that hepatic infection almost always occurs
in conjunction with azotemia; however, a recent study documented 14% of
dogs presenting only hepatic involvement, with no azotemia or
proteinuria.10
In order to prevent veterinary staff and client exposure to this
zoonotic pathogen, clinicians should suspect canine leptospirosis in the
presence of any typical or atypical clinical signs or laboratory
findings.

The lack of typical signs does not rule out the suspicion of canine leptospirosis.

Definitive diagnosis: the challenge continues despite advances

To date, no in-clinic assay is available
for rapid diagnosis of canine leptospirosis, with the microscopic
agglutination test (MAT) still being the most used diagnostic tool.1,2,3
While initial antibody titers of 1:800 in non-vaccinated dogs and
1:1600 in vaccinated dogs strongly support exposure, detection of a
4-fold increase in convalescent antibody titers is still the gold
standard. Convalescent MAT titers are required for diagnosis in
approximately half of the cases.10
Antibody titers do not correlate with disease severity and cannot
accurately determine the serovar involved. In addition, MAT results from
different diagnostic laboratories may diverge, due to the lack of
standardization among labs.12

Polymerase chain reaction (PCR) assays
are a sensitive and specific tool for early detection, but they should
be performed from both blood and urine samples of sick dogs.1
PCR better detects leptospiremia in the first 2 weeks post-infection
and better detects leptospiruria after that period. PCR is the tool of
choice for detecting urinary shedding because serology poorly predicts
Leptospira shedding in dogs.13 PCR should be preferentially used in combination with serology.3 In addition, a negative PCR never rules out infection.

MAT and PCR testing can be effectively
used to diagnose lepto, but the highest MAT titer does not confirm the
involved serovar. Negative PCR does not rule out infection.

Vaccines are safe and effective and should be used

The fact that over 60% of the cases of
leptospirosis in dogs are caused by serovars not present in bivalent
vaccines (L. grippotyphosa and L. pomona) demonstrates the importance of
using a vaccine against at least 4 serovars.4

In the largest study of its kind, 1.2
million dogs in the US were evaluated and found the current Leptospira
vaccines were not associated with an increased risk of adverse effects
within 3 days of vaccine administration.14
That study determined that young-adult, small-breed dogs that receive
multiple vaccines in one office visit are at the greatest risk of
adverse effects, independent from what type of vaccine is used.
Therefore, a reduction in number of vaccines administered at the same
visit for this population of dogs is advised.

The real paradigm shift in the last 30
years is that indoor dogs living in urban and suburban areas, even with
limited outdoor access, are at a similar risk of infection to dogs in
rural areas in contact with livestock and stagnant water. Veterinarians
should be aware of this trend when determining a dog’s risk of exposure
in order to define the best prophylactic strategy.

The cost of vaccination and risk of
adverse effects largely outweigh the cost of therapy and risk of death
by canine leptospirosis.